This invention employs resistors of doped diamond or with doping significantly below the surface by ion bombardment. Diamond and doped diamond is now established technically. Thus, Journal of Applied Physics 54(4), April 1983, at page 2106 in an article entitled "Effective p-type doping of diamond by boron ion implantation" by B. Braunstein and R. Kalish states as follows: Diamond-based semiconductor devices may turn out to be of significant importance thanks to the unique physical properties of diamond. Such devices have not been realized till now because of difficulties in doping. Standard doping techniques such as diffusion or introduction of impurities during crystal growth are hardly applicable to diamond so that the most promising way to dope diamond in a controlled way is by means of ion implantation. The successful use of this technique, however, requires finding annealing conditions which will drive the implants into electrically active sites and restore the diamond crystal structure, a task which is particularly complicated by the tendency of damaged diamond to turn into graphite.
The Japanese Journal of Applied Physics, Vol. 28, No. 5, May 1989, at page 758 in an article entitled "Electrical Characteristics of Metal Contacts to Boron-Doped Diamond Epitaxial Film" by Hiromu Shimon et al states as follows: Semiconducting diamond is expected to be an attractive material for high-frequency and high-power devices, due to its wide band gap (5.5 eV), high breakdown voltage (10E6-1IE7 V.cmE-1),(E1,2) high electron and hole mobilities (2000 cmE2VE-1sE-1 and 1800 cmE2VE-1sE-1, respectively, E(3) and high electron saturation velocity (2.times.10E7 cm.sE-1).(E4) In addition, diamond also has the highest thermal conductivity (20W.cmE-1KE-1)(E5) of any solid at room temperature, higher by a factor of 5 than that in Cu. These properties indicate that high-power, high-frequency diamond devices may surpass the performance of devices fabricated in conventional semiconductors.
Diamond film as a protective layer over the thin film resistors of a thermal printhead is disclosed in the IBM Technical Disclosure Bulletin article entitled "Thermal Ink Jet Heater Devices Incorporating Diamond-Like Carbon Films as Protective Overcoats," pp. 19-20, Vol. 34, No. 2, July 1991. The diamond layer is disclosed as being deposited in situ by various methods, including vapor deposition.